Arrangement comprising a DMS filter and a steep right edge

Abstract

In an arrangement having a DMS filter, it is provided to symmetrically divide at least one of the transducers (W) of the DMS filter (DMS) into two sub-transducers (T,T′) electrically connected in parallel and to shift them apart from each other by an amount of at least a half wavelength. This results in the signals of the two sub-transducers canceling each other out at a frequency in a stopband and thereby generating an attenuation pole in the upper blocking region.

The invention claimed is: 
     
       1. An arrangement comprising a DMS filter,
 wherein the DMS filter (DMS) has first and second converters (W 1 ,W 2 ) that are arranged alternately on a piezoelectric substrate between two reflectors (R 1 , R 2 ) and are each connected to an input or output of the arrangement, 
 wherein at least one of the transducers (W 1 , W 2 ) is symmetrically divided into two sub-transducers electrically connected in parallel, and 
 wherein the sub-transducers are shifted apart from each other by an amount of approximately one half wavelength with respect to their original position in such a way that their signals cancel each other out at a frequency in a stopband. 
 
     
     
       2. The arrangement according to  claim 1 , wherein the open clearance between the two sub-transducers that is measured from the outer edges of terminal electrode fingers of the sub-transducers that face each other is more than one wavelength. 
     
     
       3. The arrangement according to  claim 2 , wherein an acoustically non-excitatory metallization is arranged on the substrate in the open clearance between the two sub-transducers. 
     
     
       4. The arrangement according to one of the  claims 1 - 3 , wherein the two or more transducers of a type selected from a first and second transducer are available and wherein the two or more of these transducers of this type are divided in an identical or similar manner into sub-transducers. 
     
     
       5. The arrangement according to  claim 4 , wherein the DMS filter has a symmetric structure and an uneven total number of first and second transducers, wherein the divided transducer(s) is/are of the type to which also the outer transducers in the DMS filter are assigned, wherein, except for the two outer transducers, all transducers of this type are divided into sub-transducers. 
     
     
       6. The arrangement according to one of the  claims 1 - 3 , further comprising at least one series resonator connected in series to the DMS filter and a parallel resonator thereto connected in parallel. 
     
     
       7. The arrangement according to  claim 6 , wherein one coil is connected in series at the input and one at the output of the arrangement. 
     
     
       8. The arrangement according to  claim 6 , wherein a capacitor is connected in parallel to each of the serial resonators. 
     
     
       9. The arrangement according to  claim 6 , wherein the parallel resonator(s) is/are connected via a series inductor each or via a common series inductor to a ground connection. 
     
     
       10. The arrangement according to  claim 3 ,
 wherein the metallization is designed as an electrically floating or short-circuited strip pattern, and 
 wherein in each case up to n terminal electrode fingers, reflector fingers or strips of the strip pattern in all regions where two units, selected from among transducers, reflectors and strip patterns, are directly adjacent to each other, have a reduced spacing compared to the remaining regions of the respective transducer, reflector or strip pattern, wherein the distance is measured from the center of the respective finger or strip out, and wherein 3≤n≤12 is selected. 
 
     
     
       11. The arrangement according to  claim 4 , wherein all first transducers are connected in parallel. 
     
     
       12. The arrangement according to  claim 4 , wherein all second transducers are connected in parallel. 
     
     
       13. The arrangement according to  claim 4 , wherein the transducers of at least one type selected from first and second transducer are connected to a symmetrical gate.